Automatic or semiautomatic telephone exchange system



'7 Sheets-Sheet l E. P. G. WRIGHT Er AL Filed Jan. 6, 1.931-

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AUTOMATIC OR SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEM March 28, 1933.

. E Q E@ Ex E E ATTORNEY March 28, 1933. E. P. G. WRIGHT ET AL- 1.903,019

I l AUTOMATIC OR SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Jan. 6, 1951 7 Sheets-Sheet 2 Bu, n Q MYD NW A ooooooo (NAVI ATroRNEY Ml'Ch 28, En P (3l vWRlGH-r El" AL 1,903,019

AUTOMATIC OR SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Jan. 6, 1951 '7 sheets-'sheet 5 *EID OOQOOOOOMOOOOOQOWOMDO C HU. Q M h o www Y o wa Q u m S o TQ mm .OC

INVENTORS ESMOND P.G.WRIGHT BEORGE C. HARTLEY ATTORNEY March 28, 1933. E. P. G. WRIGHT ET AL 1,903,019 y AUTOMATIC OR SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed Jan- 5, 1931 7 ihee'os-Sheer, 4

1,903,019 AUTOMATIC OR SEMIAUTOMATIC TELEPHN XCHANGE SYSTEM March 28,1933. E; P. G. WRIGHT ET .AL

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AUTOMATIC 0R SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEM4 Filed Ja. 6, 19:51 7 sheets-sheet 7 ATTORNEY Patented Mar. 28, 1933 UNITED s'rATEs yPATENT OFFICE y FBMOND PHILIP GOODWIN'` WRIGHT AND GEORGE CLIFFORD HARTLEY, 0F ALDWYQH,

LONDON, ENGLAND, ASSIGNORS TO INTERNATIONAL STANDARD ELECTRIC COR- PORATION, 0F NEW YORK, N. Y.

AUTOMATIC OR SEMIAUTOMATIC TELEPHONE EXCHANGE SYSTEM Application lied January 6, 1931, Serial No. 506,884, Vand in Great Britain January 7, 1930.

diate exchanges. The subscribers in each exchange are identified b numbers, usually of four figures, and as t ese numbers are repeated in the different exchanges, code' letters, usuall three in number, are prefixed to the subscribers number and are characteristic of the exchanges to which they belong.

In order to reach the particularsubscriber from any part of the network, his number, including the code letters, is dialled, in rev sponse to which a pathto the wanted exchange must be set up, and the particular subscriber thereat selected. The selection within the wanted exchange will be carried out in response to the numerical digits in the same wa wherever the call comes from, but it is obvious that the path to be selected between the originating and terminating exchanges will differ greatly in length and direction according to the position of the exchanges in the network.

In order to select widely differin paths in response to the same code letters, t e said letters are normally dialled into a register translator at the originating exchange; the register translators at the different exchanges are differently arranged so that in response tothe same code letters they transmit the routing digits necessar for the particular path from the originating to the terminating exchan e; these routing digits may differ in num er as well as in value from the code digits dialled. It is generally unnecessary, from a technical point of view, for the numerical digits to be stored, but owing to the delay caused by the storage and retransmission of the code digits, the numerical digits are usually dialled before the terminet-ing exchange is ready to receive them, so that it is necessary to store these digits and retransmit after the inter-exchange route is complete. If, however, the selection of the `terminating exchange can be completed, und-er direct control of the calling party for instance, before the numerical digits are dialled, it is no longer necessary in normal cases to store the numerical digits.

Accordin to one feature of the present invention, t 1e selection of the numerical portion of certain inter-exchange connections is performed under direct control of the callinfr party.

L.The register translators are very complete in structure and in consequence their cost is high. Any modification of the present arrangements whereby the number of translators to be provided was substantially decreased would therefore result in a substantial reduction in the cost of installing automatic exchanges in large networks, apart from any advantages or economy in operation which might be introduced.

4 The provision of junctions voutgoing from a particular exchange in a network for intel'- exchange communication is based on the traflic density to the other exchanges in the network. Direct junctions are provided between vthe said exchangeand others to which the traffic is great, while the traffic to eX- changes, the number of calls to which is small, is passed indirectly thereto over two or more Ajunctions via one or more intermediate or tandem exchanges. It has been found by a study of the traffic conditions in the London area, that the tandeml traffic from an exchange is hardly ever morey than 10% of the total traffic outgoing from the exchange. It will be seen therefore, that if calls to exchanges directly connected to the originating exchange coul be set up independently of -the register translators, the number of register translators to be provided in the said exchange would be greatly reduced.

The main feature of the present invention consists therefore, in a circuit arrangement for an automatic or semi-automatic telephone exchange system comprisino' register translators, characterized in this that certain interexchange calls are completely set up under direct control of the calling party.

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I'j is well known that of a group of trunksA orj notions provided for dealing with a cer-v tain volume of traffic, the trafiic which actually passes over the last 20% or A30% of said lines, (according to the size of the group) is usually not more than 1% of the total traffic. It is' proposed, therefore, in the network described above, to provide to 80% only of the junctions to directly connected exchanges necessary to carry the total traffic between the exchanges, and to provide alternative trunking via tandem junctions for the 1% say of traffic tothe said exchanges for which junctions are not provided. 3y so doing, one additional tandem junction can replace a large number of said direct junctions owing to the small amount of trafiic which' the latter would carry, and the` lal` e number of tandem junctions over which t e additional calls will be "distributed, A l

l.It will be appreciated that the volume of traffic in the various interexchange junction groups varies considerably from time to time, due to extensions,y and the introduction of new exchanges. By the method of alternative trunking which is proposed these traffic variations may be handled by adjustment to the one group of junctions leading to the tandem exchange without interfering with every individual group.

It should be understood that calls which have available this alternative routing facility may normally be connected by means of direct junctions without any element of translation and it is only when all the direct junctions have been tested and found to be engaged, that the translators are brought into use. It follows, therefore, that the code switches forming part of the translators have a single set of translating terminals only for each exchange.

According to another feature of the invention a circuit varrangement for connecting one exchange to a plurality of other exchanges comprises a plurality of groups of outgoing junctions, and means whereby. a modification in the size of one of said groups will satisfy a change of traffic intensity over any one or more of said junction groups.

Since'tandemed 'connectionsare to be set up under control of a register translator, according to a further feature of the invention, calls to certain exchanges are adapted to be set up either under complete control of the calling party or by the aid of a register translator.

According to yet another feature of the invention, calls from one exchange lto another may be set up over a plurality of j unctions, over certain of which calls to further exchange or further exchanges may also beset up.

If certain junctions outgoing from an automaticexchange lead to manual exchanges provided with coder call indicators, it is necessary to translate the numerical impulses into coded impulses at 'some stage in the connection. It 1s not, however, necessary to store and vtranslate the dialled codel digits since direct junctions are selected under direct control of the calling party.

The register translators may therefore be arranged'in 'such a way that they are adapted to store and retransmit both code anrl numerical digits or numerical digits only.

In certain types of automatic telephone systems, for instance the'controller bye-path system, the inter-exchange junctions are not j directly connected to the incoming selectors, and'there is an interval after a junction has been seized "at its outgoing end before the incoming exchange is ready to receivethe next train of impulses. It'is possible in such arrangements vthat the first numerical digit may be 'dialled before the incoming exchange is ready to receive it. In 'order to deal 'with this possibility, a-signal may be sent back when the incoming exchange is ready, and if the first numerical digit is dialled before tbe receipt of this signal at the originating ex in setting up the connection, it is proposed to 'connect vup a register translator before discrimination takes place for all inter-exchange calls, and to release it unused f'the call is completed under direct control of the calling party.

According to a further feature of the invention therefore a register translator is taken into use duringthe setting up of an inter-exchange connection, and if the call is to be completed under direct control of the calling party theregister translator is re'- leased unused. j

It will be noted-that, according tothe present proposals, thev register translators are set in accordance-with'theivalue of the code digits `for tandemed connections only.

Thefinvention will bedescribed Vwith referenceftda controller bye-pathexchange, in which the first selector stageoperates inresponseto the first code digit to'sele'ct a sec; ond code bye-path circuit and conversational switch. Each second code bye-path circfuit.

comprises a switch which is adapted'tobe set by the second and third code digits; this outgoing Afrom the bye-path switch in the required direction, determines in certam cases whether av register-translator 1s required, and stores thel second and thirdcode digits for retransmission to the reg1ster- `translator if taken into use.

'provided at a tandem exchange and if the direct junctions from a tandem exchange to a terniinating exchange are ally busy, a register-translator may be taken into use, and controlvthc selection of a route via a further tandem exchange Vin response to one or more of the routing digits sent out from the first exchange.

The inventlon will be better understood from the following description taken in con- `iunction with the accompanying drawings in which Fig. 1, is a general diagram illustrating an arrangement according to the invention as applied to the controller bye path system.

Figs. 2A and 2B, 3A and 3B together constitute a circuit diagram of the second byepath common control circuit and an associated second path switch, indicated respectively at SB and 'S2 in Fig. 1. The leads at the right hand side of Figs. 2A and 2B join the corresponding leads at the left hand side of the Figs. 3A and 3B.

Figs. 4A and 4B together illustrate the circuit diagram of the register translator such as RT shown in Fig. 1.

Fig. 5, is a circuit diagram of a repeater to a tandem exchange.

Fig. 6, shows the wiring of connections between certain bank contacts of the switches R3 and R2 in the second bye path SB shown make connection by means of the associatingswitch PF with a free first path S1 tied to a second line finder LF2 which is caused to rotate to find a free first line finder LF1 having access to the calling line. It should be understood that this start signal is connected of R3 and then searches for a free outlet in that `group throu h one of the repeaters such as TR, CR or lects a free switch in the succeeding local switching stage. During the time that the switch R3 is receiving the third digit a starting signal is extended to'a number of register translators .such as RT Awhich cause their .various associating switches RF to search for the calling second bye-path. If the call is to be .tandemed the impulsing circuit will be relayed from the second bye-path SB to the register translator which will store the nui merical impulses and at the same time a preliminary translation depending upon the setting of R3 will be sent to the code switch C which has already been partly positioned under the control of the associating switch RF, the setting of which corresponds to the value of the A-digit. As soon as the code switch has been set the translated code will be sent from the sender through the associating switch RFand the switch R2 of the sec- R or alternatively sei ond bye-path to the tandem exchange. m0

lrVhen all the impulses have been sent the transmission bridge located in the tandem repeater TR is introduced and the connection set up through the switch S2, the second byepath SB and the registerl translator 'RT being released.

In the case of a call to a call indicator exchange the register translator is introduced as before, but the code switch C is not used. `When all thenumerical m'pulses'have been stored a signal is passed through the switch RF the switch R2 and the repeater CR to the manual exchange which makes a return signal when the 'sending can commence. After the sending is completed the transmission bridge in the repeater' CR is introduced and the connection established through the switch S2, the bye-path SB and the register translator being released.

In the case of a call to be handled over a direct'junction, the register transator RT will become associated with the second byepath SBbut will be released as soon as a connection is established over the switch R2 to the distant exchange. If all the junctions to the distant exchange are found to be engaged the succeeding digits will be relayed' to the register translator and the switch R2 will be moved forward to the group of outlets leadingto the tandem exchange. The

code sniitch C of the translator will be operated as already explainedv for the call through the tandem exchange and the sending will be carried out in a similar manner.

Should it happen when the switch R2 selects lectors, the impulses will be relayed to the register translator and transmitted to the distant exchange as soon as it becomes ready.

Local calls will be established throu h the switch R2 of the second bye-path but in this case there will be no facility for passing the call to the register translator if all outlets are busy.

Calls routed throu h the tandem repeater TR will be classified y means of a metering signal originated by the code switch C of the register translator and lpassed .through the associating switch RF, and the switch R2 of thel second bye-path to the repeater TR.

From the description above it will be seen that the selection at the outgoing` selector stage is always performed independently of the register-translator. According to another feature of the invention therefore an outgoing junction is taken into use during the setting u of an inter-exchange connection indepen` xntly of the register translator.

A further feature consists in this that in setting up inter-exchange calls with the aid of a register translator, the register translator does not exercise control of the setting up of a connection until a junction outgoing from the originating exchange has been seized.

The particular embodiment of the invention will now be described in detail with reference to the remaining figures of the accompanying drawings which illustrate the detail circuits of the arrangement shown in Fig. l, the switch RM1, RM2, and RM3 in these figures corresponding res ectively to the switches R1, R2 and R3 of ig. 1.

The second bye-path SB is tested from the rst bye-path FB over a circuit extending via conductor T (Fig. 3A), contacts ksl, ttl, the home position of the wiper Mn19, contacts '1164, the wiper and home position M2222 to test battery. The impulsing leads (Fig. 3B) are extended through the contacts ci?, M26, toone winding of the relay A and ground,

` and through contacts 028 and M27 to the other winding of relay A and battery. Relay A closes the obvious circuit for relay B at al (Fig. 3A). Relay B closes theobvious circuit for the relay BE via contacts 02'9 and b1.

Relay BE closes at bel ground to the test wire and removes the test battery at bell. Contact oe3 prepares the impulsing circuit of the switch RM1, the first series ofimpulses being received by the switch RM1 through contacts e4, Z263, winding of the relay C, contacts al, to ground. Relays B and C are of the slow releasing tyfpe and remain operated during the train o impulses. When the switch RM1 reaches posltion 2 a circuit is formed from ground at contacts bl through the contacts e7, wiper M2219 and the second bank contact and the home position and wiper Mn29 to the magnet RM2 and at the same time through the home osition and wiper M7235 to the magnet R 3 (Fig. 2A) throughits own interrupter springs. When RM3 stepsoli'normal, an alternative stepping circuit is formed from earth via e1, 121, off-normal bank and wiper M1235 to RM3 through its interrupter springs. The bank contacts of the wiper M2218 are wired in pairs to the contacts of the wiper M7138 so that the .wiper MnlS" when in positions 2 and 3 is in contact with position 2 of the wiper Mn38 and when the wiper Mnl8 -is in positions 4 and 5 it will be connected to the wiper M1238 in position l2 and so on. In consequence when the switch RM3 reaches position 2 a circuit is completed for the relay N from battery, winding of relay N through wiper and bank contact M7238 to the bank contact and Wiper M2218, contacts tt5, contacts r4 to ground. Relay N opens at n1 the driving circuit for the switch RM3 which remains 1n position 2 until the switch RM1 passedy to position 4 after which the switch RM3 steps to position 12 where the circuit for the relay N 1s again closed. The bank contacts associated with the wipers M1231 and M1232 are wired to the bank contactsassociated with the wi er M2220 as shown in Fig. 6 in sucha way t at each position on the bank of the s witch RM3 which represents an exchange is connected to the first of a group of contacts associated with the wiper Mn20, the remaining contacts on the banks Mn3l and M7232 being multiplied to the exchange terminals immediately following so that as soon as switch RM3 passes one set to multipled terminals marking a group in the bank of M2220 it will immediately make contact with the next set to mark the next group so that marking is applied continuously to the bank Mn20 and switch RM2 cannotoverrun switch RM3. Wiper M1232 is earthed throughout the reception of the second code digit, Via-d2, e8, so that the intermittent operation of ja3 is without eiect.

When the switch RM3 takes its first step the Wiper M1220 will make contact with the multiple extending to the first set of exchange contacts whichwill be wired to the beginning of the first group of outlets'of the switch RM2 and a circuit will be established for the relay M through contacts L9, wiper Mn20, the wiper M7231, contacts ja, d2,1'8 to ground. The relay M will open the driving circuit of the magnet RM2 established through its interrupter springs, the olf normal bank of the through contacts a2, 03, m1, g1, p1, h5 to ground. Relay E closes a locking circuit through contacts e5 to ground at be2. Contacts el open the driving circuit of the magnet RMB. Contacts e8 extend the impulsing circuit to the magnet RMB, contacts e4, complete a driving circuit for the switch RM1 through contacts t1 and the interrupter springs to ground and contacts e8 open so that if JA is operated M falls back, and switch RM2 again steps on. yA circuit was established for the relay JA while the switch RM1 was in positions 3, 5, 7, 9 and 11 and if the switch RM1 remains in one of these positions relay JA locks up through contacts ja and c7 lto ground at bl. The switch RM1 will hunt for the selected path switch SM (Fig. 3A corresponding to S2 of Fig. l) testingv from battery through the relay T and the non-inductive resistance over wiper m12 for ground on the hold wire. Relay T in operating opens the driving circuit at t1 closing the obvious circuit for the relay TT. Relay TT opens at ttl the ground on the test wire and connects it to the relay T and the removal of this ground allows the release of the preceding bye-path. The contacts 15152 and tt3 complete the impulsing circuit independently of the preceding bye-path. The third set of impulses are stored ove'r the following circuit :-battery, winding of the magnet RMB, g2, h1, cz'l, e3, be, winding of relay C, a1 to ground. When the relay C reo crates a circuit is closed forl the relay CE rom battery through contacts e2, 053, c1, b1 to ground. Relay CE locks through contacts 068, 111, 0z'2, to ground. The operation of the relay CE closes the start signal to the register translators from ground at icl through contacts ce1. It also. closes a testing circuit from the terminal T (Fig. 2B) through contacts g1, ce2, k2, to non-inductive winding of relay K. When the third code digit is complete and the relay C releases a circuit will be established for the relay TM (Fig. 2A) from battery, through contacts el, C53, 068, r1, 02'2, to ground at bl. At 25m2 a ground will be extended through contacts .7'2 4and wiper rm or 1m37 to the selected exchange terminal. The exchange terminals in the banks of m36, rm?, are connected via a distributing frame DF to one of a number of terminals AT, D, Cl, DC, and S. It the terminal on which from lead NU Fig. 3B). The contacts tml extend a grou through the contacts ja/L to the wipers m39 or 'M7230 in the banks of which each contact individual to an exchange is connected to a meter common to a number of control circuits which totals the number `ot' calls to the particular exchange. A single common meter may be provided for all dead codes.

If the selected wiper m36 or m37 rests at the end of the third code digit on the local terminal, a connection will be completed from ground, contacts m2, jal, through DF and the S terminal to the relay N and battery, and when the relay C releases a circuit will be closed for the relay R (Fig. 3B) from battery, winding of relay R, contacts r3, cell, n2, '03, m1, g1, p1, 71.5 to ground. The fact that the relay M is operated indicates that the switch RM2 is standing. on the first contact of the group marked from the wiper m31 (or m32) and relay R locks through contacts r3, m55, k7, e7 to ground at b1. The operation of relay R opens the circuit of the relay M at 1'8 causing the driving circuit of the magnet RM2 to be reclosed, opens the circuit of CE at 11 and closes at r6 and P7 the test circuit for the relays Q. and P. The switch has two sets of wipers, and tests two outlets at a time through wipers m28, m24. The contacts rl open the locking circuit of the relay CE and of'the relay TM both of which now commence to release.

If all the outlets are engaged the switch RM2 continues stepping until it reaches the last set of outlets for the group where a circuit will be completed for the relay M` through contact b9, wiper m20, contacts f8 to ground. The operation of relay M closes a circuit for the relay G (Fig. 3B) through contacts r2, 66m1, q1, p1, h5 to ground. Relay G opens the testin circuits of the relays P. and Q at g5 and q At g1 a locking circuit is provided for the relay K through contacts k2, Mtl. The opening of thezback contact at gl releases the register translator. Contacts g2 open the impulsing circuit thereby preventing the switch RM3 from taking any further steps. The contacts g6 provide busy tone through the tone condenser, contacts ce? and contacts T5 from the lead BT (Fig. 313)' When the calling subscriber releases the relay A opens the circuit of the relay B and all switches return home.

It a free outlet is found and the relay Q lasv operates from battery at the succeeding switching stage 'through the wiper m24, contacts r6, g7 winding of relay Q to round at b1; relay will open at q1 the riving circuit of the switch RMQ and close a circuit for the relay J through q1, p1, h5 to ground. Relay J closes at jl a circuit for the rela H which will close contacts h6 to provi e a locking circuit for itself and relay J from iground at be2. If wiper m23 had found rst, relay P onll would have operated, followed by relay only relay P being in turn short-circuited. The o eration of contacts k7 and `7'3 laces groun on the wiper m24: short circuitino' relay Q which releases; the connection of irect ground to wiper m24 initiate operations in the outgoing repeater as described later. The driving circuit for the switch RM2 is now opened by the contact h4, and the circuit for relay R is opened at contacts'li?. The following driving circuit is closed; batteryand ma et SM of the pathy switch, bank contact an wiper rml7,.con tacts h4, ml, g1, p1, tt5, wiper 1m18, to the interrupter springs of the magnet and ground. A marking multiple between the path switch and the switch RM2 causes the operation of the relay M through contacts h9, j2, wiper m22, the marking multiple, wiper 8171A, the wiper M7110, contacts hlO and 18 to ground. Relay M closes a circuit for the relay Gr through contacts 015, Nr.9, e6, m1, 91,711,15155 to ground through the wiper m18. The effect ofthe operation of relay G at this time will be explained later. The operation of relay H closes at h8 a circuit for the relay DH from the wiper m26, contacts i4, hh, winding of the relay DH, h8, 7'5 and wiper m28. The succeeding control switch will return a feed immediately to cause the operation of the relay DH which closes at dkl the following circu1t for the relay HH (Fig. 2B) battery and winding of relay HH, contacts dhl, c2, h3, to ground. Relay HH locks through contacts h h and k6 to ground at be2. The operation of the relay HH opens at Mil the holding circuit to the register translator and at ith?) it opens the extension of the impulsing circuit closed by the contacts h2. Contacts Mul open the circuit of the relay DC. Contacts ih andrlik? open the circuit of the relay A and extend the subscribers loop to the succeeding bye-path disconnecting the relay DH which now releases. Subsequcnt impulses are transmitted to the succeeding bye-path without causing any further operation tothe bye-path SB. The opening of the circuit of the relayrA opens in turn thecircuit for the relay B and the operating circuit of the relay BE which is retained, however, from lground on the test wiper m24. contacts i3, k7, e7, Q59, to the relay BE. The operation of the relay G already described closes a circuit for the relay HS from battery, winding of relay HS,l

wiper rml, contacts tt4, non-indiictive resistance, contacts hhS, g3, h6, be2 to ground. The relay HS extends a subscribers loop through contacts list-'5 and 11.94 to wiper cm1,

sm2. It opens at be2 the hold the circuit which is transferred to the wiper lmz3 and the contacts haii. The succeeding b e-path having received a set of impulses wi l cause its R1 switch to hunt round to make assomoved from the wiper m24 and the relay BE willrelease. Contacts bel will open the circuit for the relay- T and the relay T will open the circuit of the relay TT. The contacts be2 will open the circuit of the relays E, J and H and HH. Rela, M will release due to thel release of relays and J. Rela G will release due to the release of relays and M the homin circuit for the magnet RM2 is establishe through its interrupter springs wiper 1m29 contacts h4, m1, g1, p1, h5 to ground. The homing circuit for the switch RM1 is established through contacts e4, be3, wiper m15, contacts t1, interrupter springs and ground. The homing circuit for the switch RMS is established through its interrupter springs, the Wiper and o normal bank 1m35, contacts nl, e1 to ground'. When the switches RM1 and RM2 have returned to their home positions the testing circuit for the bye-path is re-established. v

If the switch RMS is standing at the end of the third code digit on 'a set of terminals representing another exchange reached over direct junctions, ground extended from the contacts m2 will be juin ered to terminal S causing the o eration o the relays N and R as already escribed for the local call. It may hap en that althou h a junction is found free tiie bye-path at t e incoming end is not immediately available and in consequence relay DH does not operate due to the resistance with which it is in series; this resistance is located at the outgoing repeater. When the bye-path at the incoming end becomes free the resistance in the junction is reduced and a relay in the repeater operates removing the resistance from the circuit of the relay DH. The subsequent operation is similar to the local call unless the relay DH fails to operate before the next train of impulses commences in which case a circuit is completed for the relay DC through contacts khfi, c2, h3 to ground. Relay DC locks through contacts 03, h6 to ground at be2. Contacts del close the obvious circuit for the relay CI which locks through contacts 02'2, to ground at b1. The relay CI provides an operating circuit forthe relay CE through contacts 02, c-3, g4 to ground at b1, and disconnects TM at 0L'3. The operation of the relay CE maintains at 002 the circuit for the relay K to the register translator. The first train of numerical impuses is transmitted through the contacts al, through the windin'g of C, be, e3, h2, Ma to the pulse wire to the register translator. The operation of contacts 04, provide an alternative impulse path which is established before the possible operation of the relay HH. At the end of the first numerical digit the relay C releases and provides a further chance for the relay HH to operate through contacts (Nr.1, 02 and LS to ground. If the relay HH operates ground is extended through tm, hb2, k3, 0302 to the DC lead to the register translator indicating to that circuit that sending may commence. Contacts 0717, 02'8 maintain the circuit from relay A over the subscribers loop independent of the contacts L/LG, hh7 and when the relay HH operates the circuit to the distant exchange is extended over contacts hh and hh'? to the positive and negative leads to the register translator. As in the case of the local call the path switch SM.

will be positioned by the marking multiple, relay M operating over the contacts b9 jfZ, as already described. The circuit for the relay G/cannot, however, be completed as the contacts 02'5 are opened and the contacts 1Q are also opened due to the fact that the relay R released when relay H operated. Whenthe register translator has transmitted the thousands, hundreds, tens and units impulses a ground is extended to the K wire causing the operation of relay G and causing the operation of the relay HS'. The operation of relay G opens the circuit of the relay CE at g4 and the locking circuit of lthe relay BE previously extended through the contacts 0119 and 005 to ground at b1 is opened when the contacts ce?) return to normal. The release of relay BE opens the circuit for the relays T and TT and also the relays E, J, H and HH. Contacts 'N2 and H8 open the circuit of relay A which opens the circuit of the relay B causing the release of the byepath and the register translator.

If the switch RMS is standing on a set of terminals at the end of the third code digit respresenting an exchange to which connection is established either over direct junctions or by means of tandem junctions. the ground from contacts fm2, y'al will be extended to the terminal AT causing the operation of relay AT which locks through contacts at2, 71,7, e7 to ground at b1. Contacts atl close the obvious circuit for the relay N. Relay N causes the operation of the relay R as lalready explained, relay R locking through contacts r3, m55, 056, k7, e7 to ground at b1. If a free outlet is found the call is extended as already explained, contacts L7 opening the circuit for the relay AT. If the relay DH fails to operate in time the connection-is set-up by the register translator as already explained. If all the outlets are busy the operation of the relay G closes at g4 the circuit for the relay D through contacts am. Contacts d3 cause the operation of the relay CI and both relays lock through contacts 0z'2, to ground at b1'. The circuit for relay TM is opened at 0z'3 and TM releases. Contacts at3 extend the circuit to the register translator which would otherwise be opened at the contacts g1. Contacts @i4 extend the impulsing circuit to the register translator' and contacts 02'7 and 02'8 prepare the permanent circuit for the relay A. Contacts (Z2 open the marking circuit for the relay M and close an individual marking circuit to the first outlet of the junctions. leading to the tandem exchange which will always appear as the last choices on the bank of the. switch RMQ. The operation of the contacts @i6 open the circuit of the relay R and in consequence the relays P and Q are not testing while the switch RMQ is moving forward. The opening of the contacts m1 opens the circuit for "the relay G. When the switch RM2 reaches the iirst outlet jto the tandem exchange relay M reoperates and as the relay CE has reoperated through the contacts e2, 02'3, g4 to ground at bl, the circuit is completed for the relay R through contacts 0(2-1, n2, 03, m1, Q1, p1, h5 to ground. Relay R now locks through contacts r3, at, 006, la7, e7, to ground at bl. Contacts T8 open the circuit of relay M causing the switch M712 to step forward testing for a free junction. The subsequent operation ofthe relays H and HH has already been described.

The operation of relay HH extends ground from m3 through contacts` hb2, 7c3, 0l02, d4

to the D lead to the register translator causi ing the latter to initiate the setting of the code switch which will be described in detail later. The contacts of the banks corresponding to the wipers 'M2133 and M1134 are multipled together to effect. thev primary translation of the code in the following manner. The translator switch in the registercontroller is stepped forward while ground impulses are sent to the switch RM3 therefrom. The stepping of the translator switch is dependent on the completion of a circuit over Wiper Mu?) or M1234.. The contact corresponding to a particular exchange is therefore multipled to a number of contacts to the left thereof in Fig. 2B equal to the number of steps that the translator switch is required to take to reach the corresponding set-ting. Ground is extended from theregister translator over the S leadl through contacts {a-2, the wiper and bank contact rm33 or 71711.34 contacts (il to the magnet RM3 causing the magnet to step. The stepping of' the step 0H the multiple', the preliminary translation being equal to the number of steps made by the switch RMB. When all the impulses have been transmitted from the register translator a ground is extended over the lead to operate the relay G. The contacts g3 complete a circuit for the relay HS as already described.

If the terminals on which the switch RM3 is resting after the third code digit corresponds to a call indicator exchange the ground from contacts tm2`and `y'al will be extended to the CI terminal causing the operation of the relay CI which locks as before. Contacts cz'l close the obvious circuit for the relay N causing the subsequent o ration of relay R as alread v explained T econtacts `m13 maintain the circuit for the relay CE and break the circuit for relay TM, ywhich releases. The contacts cz'8 and ci? maintain `the circuit for the relay A independent of the contacts zhy and Na7. The contacts .c1110.l

prepare a circuit for the relay HH independently of the relay DH. When a free junction is found the rela P or Q is operated resulting in the operation of the relay H or the relays H and J and round is extendedthrough contacts be2, k6, c3, d5, c7110 to operate the relay HH which locks through contacts zh. The impulsing circuit is completed through contacts m24 to the pulse lead to the register translator. vThe register translator is not adapted to send more than the four numerical digits to a call indicator exchange and in consequence the second bye-path does not'in this case send a preliminary translation to the register translator. Ground from contacts tm is extended through contacts ML2, 7c3, 02, d4 to the CI lead to the register translator. When all the impulses have been sent from the register translator ground is connected to the K lead to operate relay G causing the cut through and release as already explained.

If the terminals on which the switch RMS is resting after the third codedigit is only connected over tandem trunks, ground extended from contacts :fm2 and yal will be jum ered to the D terminal causing the operatlon of relay D which by closing its contacts d3 causes the operation of the relay CI, both relays lockin over cz'2 to ground at b1. Contacts d2 switc the marking connection from the wiper m31 (or 32) to the commencement of the tandem \gr0up causing the RM2 switch to run forward until checked by the relay M at the'commencement of the grou of tandem outlets. Contacts cz'l close the o vious circuit for relay N and when both relays N and M are operated a circuit is closed for the relay R. The operation of relay R causes the switch RM2 to test within the chosen group. When a free trunk is found the relay H is operatedr as already explained and a circuit is prepared for the relay DH. The impulsing circuit has, however, been extended to the register translator through the contacts 02'4. When the relay DH o erates a circuit is 'completed for the relay HH and an indication is sent to the register from ground at contacts m8, hb2, k3, dc2, d4 to the D lead. Subsequently the register translator will proceed with the 'reliminary translation causing the switch M3 to step forward until the wiper rm83 or Win34l leaves the multiple connected to the magnet. WhenI the register translator-has finished sending ground is extended to the K lead causing the operation of relay G and the switching and releasin operatlons are carried out as already explained. Should it happen that all the tandem outlets are engaged relay G will be operated on the last set of outlets introducing busy tone through contacts g, ce? and 7'5. The operation of the contacts g1 causes the release of the register translate f The register translator shown in Figs. 4A and 4B is capable of searching over a number of second bye-paths such as SB. It will be understood that the wipers rfl-r/O of the switch RF cooperate with the bank contacts T, S, K, P, etc. shown in Fig. 2B. The second bye-paths are divided into groups depending upon the first digit dialled by the subscriber and it is intended that the plurality of register translators shall have access to second bye-paths in a plurality of groups. All the register translators having access to one numerical group of second byepaths will attempt to make connection as soon as a calling signal is received. A calling signal will cause the operation of the re- -lay A in each register translator which is free, from battery winding of the relay A, the home contact and wiper n.94, wiper and home contact m7, the common start lead, ce1, cl, to earth. The relay A closes a driving circuit for the finder switch RF through its interrupter springs, contacta3, the home contact and wiper am of the sender switch the home contact and wiper m2,. to groundat b1. At the same time a testing circuit is prepared from ground, contacts a4, winding of relay B to the test Wiper r/Q leading to the test lead T in Fig. 2B. When the switch RF inds a bye-path in a calling condition the relay B will operate opening at bl the driving circuit of the finder switch and -closing at the same contacts a locking circuit for the relay B. Contacts b2 prepare a circuit for the relays H, J of LN. Contacts b3 place a short circuitacross one winding of the relay H and contacts b4 prepare the impulsing circuit for the numerical switch NS. When the register translator makes connection with the second bye-path it does not know initially what type of call is being made'but a ground discriminating signal is sent over one of the leads, D, CI or DC associated with the wipers ond bye-path being deenergized and relay HH being energized and relay HH being energized, and the particular wiper to which the earth is connected is determined by the condition of relays D and DC. For calls to 1 be tandemed, 4D only is operated, for C.C.I.

calls neither relay is o erated,while for numerical sending only C is operated. If the ground is extended to the wiper 1' 8 for callsv through tandem relayl H (Fig. 4 operates alone. The relay H closes the circuit for the magnet of the code switch CM throu h its interrupter springs, contacts cd2, bb3, 1, to ground and at the same time a ground is extended throu h the contacts 4 and h2 to the wiper @m5 o the code switc which tests to find the set of contacts cross connected to the wiper rf4 of the finder switch which is connected to the relay CA throu h contacts bz2. All the positions'on the ban of the finder switch associated with wiper rf4 which lead to the same group of second bye-paths which, as already explained, are characterized by the first digit dialled, w1ll be conncctedtogether and to one home position on the code sw'tch and in consequence the code switch will have one home position for each group of second bye-paths to which the register translator has access. In general the positions between the home positions will'be allocated to exchange designations which have the same first code letter. The actual position on the be completed for the rela Vso code switch is set by advancing from the' home position in accordance with the preliminary translation. If one group becomesA congested there is no technical reason why the preliminary translation described below should not advance the code switch into the group of contacts allocated for another group of second bye-paths, the'number of steps to be taken by the code switch being entirely ar- I bitrary and determined only by the number of contacts in banks m33 or m34 which are multiplied to the contact therein individual to the particular exchange designation. When the code switch reaches the home position indicating the group with whichthe finder switch RF is associated, the circuit will CA which will operate opening at ca?. the riving circuit and closing a circuit via cil, m2, N93 and b1 for the relay BB which will operate locking through contacts 653. The same ground yis extended to wiper sml, home position, contacts c62, jl, 822, winding of relay CC to battery, but there is a ossible short circuit through contacts co1, c 1 and the interrupter springs m81 to the same ground. As a result the relay CC will not operate unless the interrupter springs are open. When CC operates a circuit is completed for the relay CB through contacts ac3, ca1,ln1, bb, to ground at h1. Contacts ce2 provide a locking ound for CC throu h contacts ce1 indepen ent of the contacts c 2. Contacts cb'l extend the impulse springs through relay CZ to the wiper rf?) which is connected to the S lead to the second code bye-path and when the interand remains operated so long as impulses are being-sent through the relay CZ. Contacts cs2 impulse the magnet CM of tlle code switch causing that-switch to'advance its wipers one ste for each impulse sent tothe magnet R 3. After the switch CM has taken one step the circuit for the rela CA is opened and it releases but due to t e operation of contacts Z263, the code switch magnet CM does not get a renewed circuit. When RMB in the second byeath has stepped o the multiple indicating t e preliminary translation, there will be no circuit for the rela CZ and after a period the relay CB will release. The circuit for the' relay CC was o ened when the relay CZ is operated on the rst impulse and when the relay CB releases a circult will be reclosed through contacts c62, 7'1 and 822 but as before relay CC will not operate until the interrupter springs are opened. When relay CC reoperates it again locks through contacts ce2 and cal to ground at hl'but as the relay CA has now released there is no circuit for the relay CB and when the interrupter springs remake the ground is extended through contacts'cbl and ce1 to the sender switch SM. The sender switch makes one step and in position 2 a circuit isclosed for the relay SA through contacts i2, second bank contact and wiper cm1 to ound at h1. Relay SA o ens at 8c2 the s ort circuit across 'the negative and positive lines which are now only connected by means of the pulse springsi through contact ce1. CBvis of the slow to release type- LS which open once for every impulse sent to the magnet SM.l The contacts in the banks of wipers cm1-cmd which correspond to the various exchanges to be reached via tandem are jumpered tothe required contacts 3-12,

1li-'23, 25-34, and 26-35 inthe bank ofwiper m2. When the required number of impulses have been sent according tov the translation switch SM will be in any one of positions 3--12 and ground is extended through the contacts 9'4, h2, wipers cm1 and cm2, contacts ssl to the relay SZ and battery. Relay SZ locks through contacts sal and sal. Contacts 8.25 replace the short circuit across the loop springs LS, and contacts .924 provide a driving circuit for the switchSM through its interrupter springs, 824, 7'2, to the bank contacts and wiper cm1 which is still connected to ground at h1. In this way the sender switch drives to position 13 where the circuit lll for-the relay SA and the magnet SM is opened. The operation of contacts ce2 open the circuit for the relay CC which has, therefore, been released. The relay SA is of the slow to release type and falls back slowly. The relay SZ also falls back slowly after the release of relay SA. When the relay SZ releases, the `circuit for the relay CC is reclosed and the sequence of operations is repeated except that the relay SZ is operated over a jumper between one of the bank contacts associated with the wiper cm2 of the code switch and one of contacts 14--23 of .sm-2. Relay CC is again reoperated in position 25 and the relay SZ operated from one of the jumpers associated with the wiper cm3 of the code switch. If there is a fourth translated digit this will be obtained in the same way from the wiper CM4 of the code switch but should there be no fourth translated digit, wiper CM4 will be connected through its bank contact to the CO terminal which is wired to the bank contact No. 37 associated with the wiper cm2. This ground will be extended through the wipcr SM2 and the contacts 823 to the magnet SM and to the relay SA causing the sender switch to advanceimmediately to position 49 and preventing release of relays SA and SZ in position 37. It it is required to send only one translated digt the corresponding contacts in the banks of wipers cm2, and cm3 and omet will be jumpered to the CO terminals numbers 13, 25, 37

respectively by which means the sender switch will advance to position 49 after thc first digit has been set.

During the time that the code switch has been set and the translated digits have been sent the numerical impulses have been received and may be retransmitted. The impulsing circuit for the numerical switch NS, contacts ds2, the vwinding of relay C, contacts 64 to the wiper 1'f5 making connection with the pulse lead. The switch NS takes one step for each impulse and the relay C which is of the slow torelease type remains operated during the series of impulses. Contacts c3 close the obvious circuit for the ,relay DS which is also of the slow to release type.

.When the relay C releases a transitory circuit is completed from ground at 61 through contacts e1, cia3, to the wipers m4, 5, 6, and 7 whlch will cause the o eration of a certain combination of the re ays WA, WB, WC andWD dependingupon the digit dialled. A locking circuit provided for each relay through contacts such as wa4 to ground at 61. When the relay DS releases the storage operating circuit is opened at s3 but a driving circuit for the numerical switch NS is closed through its interrupter springs, contacts s/1, bank contact and wiper ns1 to ground at 6l. This circuit is maintained until the numerical switch reaches position 12 where it remains waiting for the next set of impulses.

The relays XA, XB, XC and XD are operated in a similar manner for the hundreds digit and the relays YA, YB, YC and YD for the tens digit. The units digit is stored by the numerical switch NS and in this position the relay DS is maintained after the relay C releases through the bank contact and wiper Nsl t0 round at 61. The continued operation o? the relay DS opens at s2 the impulsing circuit and prevents any further movement of the numerical switch NS in response to the subscriber dialling. The condition of relay operation for the thousands digits is such that either the relay WA or WC is always operated and in consequence when the thousands impulses have been received a ground will be extended from h1, 663, the wiper laml, bank contact 49, wal (or wel) 7'3 jl, .922 causing the reoperation of relay CC. The thousands impulses are now sent out, SM being stepped on in synchronism. The relays SA and SZ operate, as already described, the ground for operating relay SZ bein connected b contacts of the relays WA, B, WC or D. The'circuit for re-energizing the relay CC in posi-tion 6l is dependent u on the contacts wal and wel, the correspon ing circuit for relay SZ beingxcomlpleted throu h contacts of the relays X X ,g XC and D. In position 73 the circuit for relay CC is established through contacts yal or yal and the circuit for relay SZ through contacts of the relays YA, YB, YC and D. As has already been explained the relay DS remains operated after the units digit and thecircuitl for the relay CC in position 84 is established through contacts dal and yal or yal. The circuit for the relay SZ is established by the position of the numerical switch NS, ground being extended from 61 through 01, s3 and'wiper m6 to the relative bank contact associated with wiper cm2. In position 96 a ground is extended from h1, 663 through the wiper sml to the wiper rfl which is connected to the K lead to the second bye-path and causes the operation of the relay G in that circuit. The second bye-path extends the talking conductors and subsequently opens the circuit for the relay B which releases. Contacts 62 open the circuit for relay H but the short circuit provided by the contacts 68 is removed from the second winding of the relay H which,

will remain operated so long as there'is a feed and MB. In this way jumpering contacts are adaptedto be connected either to the terminal MA, the terminal MB or through a resistance to the relay A. The operation of relay A makes ground throu h contacts a1 and a2 to both the terminals A l articular to each set of code .terminals may completed so as to Iground the terminal MA or the terminal M or both terminals. The circuit for the relay BB was opened at h1 when the relay H released but bemg of the slow to release type it ydoes not release immediately and the metering potential is maintained until relay BB releases. The contacts h1 open the circuit for rela DS and when this relay releases the numerical switch NS returns to its home position through its interrupter springs, contacts dal, the oil normal bank and wiper m2 to ground at b1. The sending switch SM returns home through its interrupter'springs, the olf normal bank and wiper ami, the home position and wiper In.92 to` ground at b1.

If the register translator is required to complete a call' over a direct junction no translation being necessary ground is connected to wiper of 6 and the relays H and LN operate together when HH in the byepath energizes. The contacts ln2 switch the circuit for the relay CA to a particular set of contacts associated with the code switch CM so that thecode switch takes-up a position independent of the setting of t e finder switch RF. Contacts Zul open the operating circuit of the relay CB which would otherwise be closed when relay CC operated. The bank terminals associated with the wipers cm1, cm2 cm3, cm4 in this position are jumpered to the CO terminals 1n positions 2, 13,

25 and 37 so that a circuit for the relay SZ is completed at the same time as the circuit for the relay SA and in consequence the short circuit across the impulse springs LS1 is maintained.y The sender switch advances immediately to position 49. The storinff and sending of the numerical im ulses-is identical with the operation alrea y described.

If the register translator is to be used for completing a connection to a call indicator exchange, the relay J is operatedover wiper v '1K7 The contacts 7'4 complete a circuit for t e relay BB through contacts cjl. The same ground is extended through the wiper sml, contacts cb2, contacts jl, through the interrupter springs MS2 to the sender switch SM causing that switch to take one ste In position 2 ground is extended throng.,r contacts 7'2 and 7'1 to the interrupter springs and the stepping is maintained until the switch reaches position 49. In this position the Sender switch waits until all the numerical impulses have been received at which time explained. The relay to the negative wiper rf9. This signal causes an o eration in the manual exchan e and when t e de-coding equipment is avai able the battery on the ne ative lead is removed. The operation of t e rela CJ opens the circuit for relay BB which re eases roviding an alternative circuit for relay C independent of the wiper 8m5 and also completes the ste ping circuit from ground at i4 through wlper sml, contacts wal or w01, bbl, jl, 'and the interrupter springs MS2 tol the magnet SM: The sender switch advances to position 61 and. waits in this position until the de-codin equipment is ready at which time the relay J releases as already BB in reoperating disconnects the relay CJ from the negative line and closes a further stepping circuit through` contacts alor m01 and bbl. In position 62 the code sending commences, ground being connected to the positive wiper and battery being connected to the negative wiper if the relay WA is normal. In position 63.l the negative line is connected to ground and the positive line to light or heavy battery depenldin upon the condition of the contacts fw nected but in position 65 the positive line is grounded and the negative line connected to attery if the relay WC is normal. In position 66 the negative line is grounded and the Eositive line is connected to light or heavy atterydepending upon the condition of the contacts wall. In positions 67-72 `further impulses 'are sent depending upon the condition of relays XA XB, XC and XD and in positions 74-79 further impulses are sent deending upon the condition of relays YA, Y YC and YD. In osition 8O the negative line is connected to battery and the positive line is connected to certain positions of the bank m4., These positions are complementary to the positions connected to the relays WA, XA, YA. In position 81 the positive line is connected to battery through a low resistance and the negative line is connected through wiper n.95 to ground in such a way that there will be no additional resistance unless the units-digit be of a value that the relays WB, XB and YB would not operate. As a resulta heavy negative lpulse will be sent for certain digits and a llght negative pulse for other digits in the sameway as adiscrimination is made by the contacts wbl. In position 82 both linesl are disconnected. In position 83 a positive pulse is sent through bank contacts and wiper n.34 in such positions that correspond to digits which would not operate the relays WC, XC and YC. In position 84 a 1ight`or heavy negative pulse is sent by means -of the position of the wiper n.97. In position 85 and later position the positive and negative-lines are left disconnected. In position 96 the ground through contacts i4 and the wiper cm1 is connected n position 64 both lines are discon- A through wiper Tf1 to the K lead causing the operation of the relay G of the second byepath. Relay G switches through the conversational conductors and causes the release of relay J. The homing circuit for the switches NS and SM will be ,as already described for a normal call.

The repeater to tandem shown in Figure 5 will be operated in the following circuit The testing circuit will be through the byepath test conductor BPT, contacts hs4, be2, to battery. After seizure ground will be extended over the bye-path test causing the operation ofthe relay BS and a circuit will be completed for the relay JS through con` tacts bel, L82 and jsl. Relay HS is shunted and does-not operate at this time. The impulse circuit is extended through contacts hel and L83` through the repeater circuit without repetition. After the impulses have been sent ground is extended to the hold wire if the connection has been routed throu h an operators position and no transm1ssion bridge is required. In such case the relay JS is short circuited and closes the circuit for the relay HS through contacts 7'84. Relay HS opens the bye-path testing circuit at contacts hell and the relay BS releases. Contacts hel and zs3 connects the BP and BP- leads to the relays MZ and MX respectively which are /connected to battery. A combination ofthe relays MX and MZ are operated but/owing to the fact that relay BS is released the relays MX and MZ are not maintained after the register has been disconnected. For a normal call the relay JS is not short circuited and the relay AS o perates over the contacts 82 and js. Relay B is locked over contacts asl. Contacts as2 close the obvious circuit for relay HS through contacts del. The` contacts as3 a'nd as4 complete the conversational circuit through the retard IS and the shunt field relay DS. The operation of the contacts hsB and Lsl complete the circuit to the relays MX and MZ one, or other,or both of which may operate and lock over contacts 'm81 or` m21 and 583 to ground. The ground is extended to the start lead S to common metering equipment through contacts hs, mm2 or m22. When the circuit for the relay HS is opened through the operation of the shunt field relay DS. The common metering equipment makes connection with the circuit requiringmeteringand receives a discriminating earth over contacts mm3 and/or mz3 and hs. A fourth condition may be signalled if neither MX nor MZ is operated. Booster potential is applied once or more via lead B to the hold wire in consequence. The relavs MX and MZ are short circuited via lead SC at the time of metering to remove the ground from the start point. When the calling subscriber releases thcccontacts asl open'the circuit for relay BS and the contacts bal retween one exchange and another, means for establishing an indirect connection between said exchanges under control of said register translators, and means whereby calls over said direct connection may be set up independently of said register translators under direct control of a calling party.

2. A telephone system as claimed in claim 1 in which for all inter-exchange calls a reg-l ister translator at the calling exchange 1s connectedfor use and means 1s provided to release said register translator unused if a direct connection between one exchange and another is available.

3. In a telephone system comprising a first exchange, a plurality of other exchanges and a tandem exchange, the combination of a register translator at said first exchan e, direct junction lines between the first-exc ange Aand said other exchanges, junction lines between the tandem exchange and said first exchange and said other exchanges, means whereby a calling party at said first exchange may establish a connection automatically to a called party at any one of 'said other exchanges over said direct junction lines independently of said register translator, and means `operative if all the direct junction lines between said first exchange and the exchange of the called party are busy, to cause said register translator to establish an alternative connection to the desired exchange via said tandem exchange.

4. A telephone system as claimed in clalm 3 wherein the number of direct j unctionlines between the first exchange and each of said other exchanges is substantially less than the number necessary to carry the traffic between said exchanges and the number of junction lines 'between the first exchange and the tandem exchange is lsufiicient to carry the trafiic between the first exchange and said other exchanges for which direct junction lines are not rovided, in addition to other tan dem tra c from said first exchange.

5. A telephone exchange system, according to claim 3 wherein a plurality of junction groups is provided from one exchange to a plurality of other exchan es and-means is provided whereby a modi cation lto the size of one of said groups will satisfy a change of trafiic intensity on any one or more of said junction groups. i

6. In a telephone system comprising a first exchange, a plurality of other exchanges and a tandem exchange, the combination of a register translator at said first exchan e, direct junction lines lbetween the first exc ange and said other exchanges, junction lines between the tandem exchange and said first exchange and said other exchanges, means independent of said register translators for selectin one of said junction lines'from said first exc ange on an inter-exchange call and means whereby'the re ister translator controls the setting up o the connection over certain of 'said junction lines.

7. In a telephone system comprising a plurality of exchanges and junctionlines interconnectin said exchanges, the combination at one ateast of said exchanges of a plural- @ty of discriminating circuits each of which is associated with a plurality of-talking circuits, a plurality of register translators each associated with a plurality of said discriml inating circuits and means in said discriminating circuits which determine whether or not a register translator is to be used in setting up a connection. l

8. A telephone exchange system, the combination of sin le motion selector switches,a number of tal in circuits, a plurality of control circuits eac of which is associated in common with a plurality of talking circuits, a plurality of register translators each associated in common with a vplurality of control circuits, each control circuit comprising discriminating means which is adapted to respond to a code digit or digits and to determine whether a register translator is to be used in setting up a connection.

9. A telephone system according to claim 8 wherein each control circuit comprises aA bye-path switch which is adapted to select a free outlet in a wanted direction and means is provided for extendin an impulsing circuit over the selected out et either from the calling partys circuit or from the sending circuit of a re 'ster translator.

10. In a te ephone exchange system the combination of a first group selector, a plurality of second group selectors accessible from said first grou selector, inter-exchange junction lines to different exchangesv accessible respectively to said second group selectors, inter-exchange 'unction lines to the same exchan e accessible to all of saidsecond group se ectors and register translators associated with said second group selectors and adapted to control the setting up of calls over said last mentioned junction lines.

11. In a telephone exchange system, the combination of single motion switches, a control circuit common to said switches, a register translator comprising a code switch adapted to receive a plurality of code digits, a switch in said control circuit adapted to receive a plurality of code digits, said switch being inter-connected with said code switch whereby the number of translating positions path circuits each associate provided on the code switch is less than the number of exchanges to which access is possible from said single motion switches.

12. A telephone exchange system according to claim 3 wherein cal s between certain exchanges can be set up over direct junctions between the originatin and terminating exchanges or via in irect junctions through -an intermediate exchange or exchanges and the number of indirect junctions outgoing from an exchange, over which a 4 particular terminating exchange is accessible is greater than the numberlof direct tions to a distant exchange and to a group ofindirect junctions over which access to the same distant exchan ma be obtained, means for causingfsai switc to search over said direct junctions and if none of said 'unctions is free to continue automaticall' to search over said indirect junctions, a re ster translator, and discriminating means a apted to cause said register translator to control the setting up of a connection over said indirect junctions.

15. Ina telephone exchange system comprising register translators, means whereby an inter-exchange connection may be set up independentl -of said register translators, means where y the register translators are adapted to store numerical digits only in the event the direct connection to the distant exchange is not established for the receipt of dialled impulses and' means in said register translator responsive on the establishment of said connection in the distant exchange to cause said register translator to re-transmit said numerical digits for setting up the connection in the distant exchange.

.16. In a telephone exchan e system comprising automatic and lmanual exchanges interconnected by junction lines, the combination at said automatic exchanges of register translators, means for settin u inter-exchange connections independlmtly of said register translators under control of a calling party, means for establishing a connection between an automatic exchan e and a manual exchange, and means in sai register translatornoperative on connection to a manual exchange to translate the numerical digits ofl a wanted number into code impulses for transmission to said manual exchange.

l17. In a telephone exchange system the combination of a lurality of selector switches and talking circuits, a (plurality ofbyein common with 

